WEBVTT FILE ﻿1 00:00:00.000 --> 00:00:03.003 [music throughout] 2 00:00:18.551 --> 00:00:20.887 The Trojan asteroids are found in Lagrange points, 3 00:00:21.321 --> 00:00:25.058 which are these special places that lead or follow a planet in its orbit 4 00:00:25.392 --> 00:00:30.230 by 60 degrees, and it's sort of where the gravitational force of the planet 5 00:00:30.230 --> 00:00:33.733 and the gravitational force of the Sun all cancel out. 6 00:00:33.767 --> 00:00:37.504 So if you put an object there, it will stay there for a long period 7 00:00:37.504 --> 00:00:38.905 of time, basically forever. 8 00:00:38.905 --> 00:00:42.375 So when we see objects there, these are objects 9 00:00:42.375 --> 00:00:45.945 that we know were in place a very long time ago. 10 00:00:48.081 --> 00:00:49.182 So if you just take 11 00:00:49.182 --> 00:00:52.685 a random asteroid and just put it in the outer Solar System, 12 00:00:52.685 --> 00:00:54.421 the gravitational force 13 00:00:54.421 --> 00:00:58.291 of the four outer planets will just clear them out in a very short period of time. 14 00:00:58.925 --> 00:01:00.727 So they'll basically be gone. 15 00:01:00.727 --> 00:01:04.564 So the only places it turns out in the outer Solar System 16 00:01:04.564 --> 00:01:08.368 where you can find stable regions are these Lagrange points. 17 00:01:08.401 --> 00:01:13.173 Lucy in particular, is going to go after the Jupiter Trojans. 18 00:01:13.473 --> 00:01:16.276 We're trying to see a type of object 19 00:01:16.643 --> 00:01:21.448 that represents and constrains the formation of the outer planets. 20 00:01:21.915 --> 00:01:26.820 And you need to go to these Lagrange points in order to see that kind of thing. 21 00:01:28.221 --> 00:01:29.722 One of the really groovy 22 00:01:29.722 --> 00:01:35.662 aspects of our mission is its trajectory, because we're visiting 23 00:01:35.929 --> 00:01:39.399 a record number of objects like these Trojans. 24 00:01:39.899 --> 00:01:43.903 And we do that with this very complicated dance, particularly in the beginning, 25 00:01:43.970 --> 00:01:49.642 where we are using the earth actually as a gravitational slingshot. 26 00:01:49.876 --> 00:01:53.580 So Lucy will start off in an orbit very similar to the Earth, 27 00:01:53.847 --> 00:01:58.518 and then gravitational encounters with the Earth will actually pump it up. 28 00:01:58.518 --> 00:02:02.422 So it gets out to the Lagrange points near Jupiter's orbit. 29 00:02:03.323 --> 00:02:06.493 So if you're going to understand how planets like the Earth formed, 30 00:02:07.327 --> 00:02:09.762 you have to understand how the bigger planets 31 00:02:09.762 --> 00:02:13.233 which sort of dominated the whole process came to be. 32 00:02:13.233 --> 00:02:15.435 And that's what Lucy is going to do.